The purpose of this project is to study the action of fluoride on various systems used to detect clastogenic or mutagenic substances. To data fluoride has been examined in microbiological assays used to detect mutagens and found to be non mutagenic. No effects on chromosome structure were noted in animals given widely different levels of fluorides. DNA repair after X-ray was unchanged by fluoride. No genetic effects of fluoride were noted in a recessive lethal test of fluoride on drosophila. The data indicate that fluoride has no mutagenic activity.